i think this is ok . after lupdate i use this command : linguist my_da.ts . i write my translation and click on "mark item as done and move to the next unfinished item" then click on "save all" and close the linguist.
then i write in cmd lrelease empty.pro and my output is :

Hi,
If I have to add I do something like this:lupdate . qml -ts untitled1.ts untitled1_pl.ts
lupdate will scan all h , cpp and qml files in current directory "." and "qml" directory and search for any strings enclosed in tr or qsTr and store them in given ts files (default English and Polish in this case)

lrelease untitled1.ts untitled1_pl.ts
This will generate .qm files for languages specified by given .ts files.